Non-Vented Bladder System for Curing Composite Parts

ABSTRACT

A composite part charge having an internal cavity is placed on a tool and covered by a vacuum bag for autoclave curing. A bladder is placed in the cavity to react autoclave pressure on the charge. The bladder is coupled with a flexible fluid reservoir located beneath the vacuum bag. The bladder is pressurized by autoclave pressure applied through the vacuum bag to the flexible fluid reservoir.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of and claims the benefit of priorityto U.S. patent application Ser. No. 13/491,698, filed on Jun. 8, 2012,and entitled “Non-Vented Bladder System for Curing Composite Parts”, theentire contents of which are incorporated herein by reference.

BACKGROUND INFORMATION

1. Field

The present disclosure generally relates to methods and equipment forfabricating composite resin parts, and deals more particularly with abladder system used in curing composite parts within an autoclave.

2. Background

Composite resin parts may be cured within an autoclave that applies heatand pressure to the part during a cure cycle. Some part geometriesinclude internal cavities that may cause the part to collapse underautoclave pressure unless a tool such as an inflatable bladder is placedin the cavity to react the autoclave pressure force applied to the part.For example, in the aircraft industry, inflatable bladders may beinserted into the cavities of composite stringer layups that areautoclave cured on mandrel-like cure tools. These bladders arepressurized by venting them to the autoclave pressure.

There are several problems with the vented bladders described above thatmay lead to inconsistencies in the cured parts. For example, failure toproperly vent the bladder may prevent the bladder from becomingpressurized sufficiently to react the applied autoclave pressures.Similarly, insufficient bladder pressurization may result from thefailure of sealant tape used to seal a vent hole coupling the bladderwith an outside vent. It is also possible for a bladder wall to fail orbe penetrated, in which event autoclave gases may be forced into thepart throughout the cure cycle. These issues may be particularlyproblematic where a relatively large number of stringers are cocured atthe same time with other parts. For example, where a number of stringersare cocured with a fuselage skin, each of the bladders placed in thestringers is a potential source of leakage into the cocured structurethat may cause the entire structure to be scrapped or extensivelyreworked.

Accordingly, there is a need for a non-vented bladder system that mayreduce or eliminate the adverse effects resulting from leaks in thebladder or failure to properly pressurize the bladder. There is also aneed for a bladder system and curing method that does not requireventing to autoclave pressure, and which may eliminate the need forbladder vent hole seals.

SUMMARY

The disclosed embodiments provide a non-vented bladder system that maysubstantially reduce or eliminate inconsistencies in cured parts due tobladder leakage, seal leakage and/or or failure of a bladder to properlyvent to autoclave pressures. The disclosed system may reduce productscrap and/or the need for rework. Additionally, the disclosed method andnon-vented bladder system may reduce labor costs and improve productionflow. The embodiments eliminate the need for use of a sealant tapearound a vent hole in the bladder. A fluid reservoir is permanentlyattached to the bladder vent hole and is sealed beneath a vacuum bag,thereby eliminating leak paths around the bladder vent. The reservoirpressurizes the bladder cavity when the autoclave is pressurized. In theevent of a leak in the bladder, only the volume of the bladder is leakedinto the part.

According to one disclosed embodiment, apparatus is provided for use inautoclave curing of a composite part charge having an internal cavity.The apparatus comprises a flexible bladder adapted to be placed in thecavity for applying pressure on the composite part charge during thecuring, and a reservoir of fluid for pressuring the bladder, thereservoir and the bladder being coupled together in a closed system. Theapparatus may further comprise a flexible bag sealed over the flexiblebladder and the fluid reservoir, wherein the flexible bag is inface-to-face contact with the fluid reservoir and transmits pressurefrom the autoclave to the fluid reservoir. The apparatus may alsocomprise a cure tool adapted to have the composite part charge placedthereon, and wherein the fluid reservoir is located on the cure tool andthe flexible bag is sealed to the cured tool. The fluid reservoir isflexible. The bladder includes a vent hole, and a portion of the fluidreservoir is attached to the bladder and includes a fluid outlet coupledwith the vent hole in the bladder. The fluid reservoir may include avacuum port sealed beneath the flexible bag adapted to be coupled with avacuum source for selectively relieving pressure within the fluidreservoir after the composite charge has been cured. The bladderincludes a septum forming an interior chamber within the bladder, and afill material filling the interior chamber which has a density that issufficient to stiffen the bladder when the bladder is pressured by fluidfrom the fluid reservoir. The septum includes a flexible side that isexposed to fluid from the fluid reservoir. The flexible side flexes toapply pressure to the fill material when the fluid reservoir pressurizesthe bladder.

According to another disclosed embodiment, a non-vented bladder systemis provided for use in autoclave curing a composite part charge. Thenon-vented bladder system comprises a bladder adapted to apply pressureto the composite part charge, and a flexible fluid reservoir adapted tocontain a quantity of fluid and compressible by pressure applied by theautoclave for supplying fluid pressure to the bladder, wherein the fluidreservoir is coupled with the bladder in a closed fluid system that isnot vented to the autoclave. The fluid reservoir is attached to thebladder. The fluid reservoir includes a fluid outlet, and the bladderincludes a vent hole coupled with the fluid outlet. The bladder includesflexible septum exposed to fluid from the fluid reservoir forming aninternal chamber within the bladder, and a fill material within theinternal chamber for stiffening the bladder.

In another embodiment, apparatus is provided for applying substantiallyuniform external air pressure on an uncured part having an internalcavity. The apparatus comprises a tool adapted to have the part placedthereon, a bladder adapted to be placed within the internal cavity andin contact with the part, the bladder being adapted to be pressurizedwith a fluid, a reservoir of the fluid coupled with the bladder, and aflexible bag sealed to the tool and covering the part, the bladder andthe reservoir. The reservoir is attached to the bladder to form a singleassembly that may be installed in and removed from the internal cavity.The reservoir includes flexible walls in face-to-face contact with theflexible bag allowing the external pressure to be applied to thereservoir through the flexible bag. The bladder includes fill materialfor stiffening the bladder, and a septum separating the fill materialfrom the reservoir fluid. The reservoir and the bladder form a closedfluid system that is not vented to the external pressure.

According to still another embodiment, a method is provided of autoclavecuring a composite part charge having an internal cavity. The methodcomprises placing the composite part charge on a tool, installing abladder within the cavity, coupling the bladder with a reservoir offluid, sealing a flexible bag over the part and the reservoir, and usingthe flexible bag to transmit autoclave pressure to the reservoir toforce fluid from the reservoir into the bladder. Coupling the bladderwith the reservoir includes attaching the bladder to the reservoirbefore the bladder is installed in the cavity. Sealing the bag includessealing the bag to the tool. The method may further comprise stiffeningthe bladder by filling the bladder with a fill material, and separatingthe fill material from the fluid by placing a septum in the bladder. Themethod may also comprise using a vacuum to draw the flexible bag downagainst sides of the reservoir.

According to a further embodiment, a method is provided of autoclavecuring a composite part charge having an internal cavity. The methodcomprises supporting the composite part charge within the autoclave, andpressurizing a bladder within the internal cavity using autoclavepressure to force fluid from a fluid reservoir into the bladder. Usingthe autoclave pressure to force the fluid from the fluid reservoir intothe bladder includes evacuating a vacuum bag sealed over the fluidreservoir, and using the bag to transmit the autoclave pressure to thefluid reservoir.

The features, functions, and advantages can be achieved independently invarious embodiments of the present disclosure or may be combined in yetother embodiments in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the advantageousembodiments are set forth in the appended claims. The advantageousembodiments, however, as well as a preferred mode of use, furtherobjectives and advantages thereof, will best be understood by referenceto the following detailed description of an advantageous embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a functional block diagram of a non-ventedbladder system according to the disclosed embodiments.

FIG. 2 is an illustration of a perspective view of a composite resinstringer cured using the non-vented bladder system shown in FIG. 1.

FIG. 3 is an illustration of a perspective view of a cure tool used incuring a composite stringer charge.

FIG. 4 is an illustration similar to FIG. 3 but showing a stringercharge having been placed on the tool.

FIG. 5 is an illustration similar to FIG. 4 but showing an inflatablebladder having been placed within the cavity of the stringer charge.

FIG. 6 is an illustration similar to FIG. 5 but additionally showing askin charge having been placed on the stringer charge.

FIG. 7 is an illustration similar to FIG. 6 but showing a caul platehaving been installed over the skin charge.

FIG. 8 is an illustration similar to FIG. 7 but showing sealant tapehaving been applied around the periphery of the cure tool.

FIG. 9 is an illustration of a perspective view of one end of the curetool shown in FIG. 8, a flexible fluid reservoir having been installedon the cure tool and coupled with the flexible bladder.

FIG. 10 is an illustration of a sectional view taken along the line10-10 in FIG. 9, but additionally showing a vacuum bag having beeninstalled over and sealed to the cure tool.

FIG. 11 is an illustration of a sectional view similar to FIG. 10 butshowing an alternate embodiment employing a septum within the bladder,the bladder being shown in its unpressurized state.

FIG. 12 is an illustration similar to FIG. 11 but showing the bladderhaving been pressurized through autoclave pressure applied to the fluidreservoir through the vacuum bag.

FIG. 13 is an illustration of a diagrammatic view showing the volumes offluid reaching the composite charge in the event of a leak in thenon-vented bladder system.

FIG. 14 is an illustration of a flow diagram of a method of autoclavecuring a composite part charge having an internal cavity using anon-vented bladder system.

FIG. 15 is an illustration of a flow diagram of an alternate method ofautoclave curing a composite part charge using a non-vented bladdersystem.

FIG. 16 is an illustration of a flow diagram of aircraft production andservice methodology.

FIG. 17 is an illustration of a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring first to FIG. 1, an uncured composite resin part 20, hereafterreferred to as a “charge”, a “composite charge”, a “composite partcharge” or a “stringer charge”, is cured on a cure tool 22 placed in anautoclave 26 in which autoclave heat and pressure are applied to thecomposite charge 20. The composite charge 20 includes one or moreinternal voids, trapped or enclosed areas, or cavities, which for easeof description, will collectively be referred hereinafter as a cavity28. A flexible, inflatable bladder 30 is placed within the cavity 28prior to a cure cycle in order to react autoclave pressures applied tothe charge 20 during curing. A flexible fluid reservoir 32 is mounted onthe cure tool 22 and is coupled with the bladder 30 in an manner thatforms a closed bladder system 25 which is not vented to the atmospherewithin the autoclave 26. In other words, the bladder 30 and the fluidreservoir 32 form a closed fluid system that is not directly exposed tothe internal atmosphere of the autoclave 26. A flexible bag, such as avacuum bag 24, is placed over and sealed to the cure tool 22, coveringthe composite charge 20, the bladder 30 and the fluid reservoir 32. Theflexible bag 24 is adapted to be coupled with a suitable vacuum source64 for evacuating the flexible bag 24. During curing, the bladder 30 ispressurized using a substantially non-compressible fluid (not shown)supplied from the fluid reservoir 32.

As will be discussed in more detail below, because both the bladder 30and the fluid reservoir 32 are located beneath the vacuum bag 24, thebladder 30 is not vented to the internal atmosphere of the autoclave 26,i.e. the bladder 30 is non-vented. Rather, the combination of thebladder 30 and the fluid reservoir 32 form a closed, non-vented bladdersystem 25 that is controlled by autoclave air pressure exerted on thevacuum bag 24. Optionally, the bladder 30 may include an internal septum35 that separates substantially the full internal volume of the bladder30 from the fluid supplied from the fluid reservoir 32. Reduction of thepressure within the fluid reservoir 32 allows the bladder 30 topartially collapse slightly, thereby preventing the bladder 30 frombecoming “locked” in the composite charge 20 and facilitating easyremoval of the bladder 30 from the cured composite charge 20.

Referring now to FIG. 2, the disclosed non-vented bladder system andcuring method may be employed to cure any of a variety of compositeresin parts of various geometries, having one or more internal cavities.For example, and without limitation, the disclosed system and method maybe used in the fabrication of a fiber reinforced composite resinstringer 23, which may comprise a multi-ply layup of prepreg. Thestringer 23 includes a hat section 27 forming an internal cavity 31, apair of laterally extending flange sections 29 and a substantially flatskin section 33 that is consolidated together with the flange sections29 during curing. Other stringer geometries are possible.

FIGS. 3-10 respectively illustrate successive stages in the preparationof the apparatus shown in FIG. 1 for curing of the stringer 23 shown inFIG. 2. Referring particularly to FIG. 3, a cure tool 22 made of anysuitable material includes an internal cavity 28 defining a hat sectiontool face 32, and a pair of laterally extending, flange section toolfaces 34. Tool faces 32, 34 are configured to respectively match thegeometry of the hat section and flange sections 27, 29 respectively ofthe stringer 23. The cure tool 22 has a substantially flat upper toolsurface 36 surrounding the internal cavity 28, a chamfered surface 38 atone end of the cavity 28, and a substantially flat end section 40. Oneend of the internal cavity 28 is open at 42. As will be discussed below,the cure tool 22 may be used to assemble composite stringer charges, andto cure the assembled charges within an autoclave 26 (FIG. 1). While theillustrated cure tool 22 has a geometry that is adapted to matchfeatures of the stringer 23, it should be noted that the disclosednon-vented bladder system 25 may be used with cure tools having any ofvarious other geometries, depending on the application and theparticular composite part charge to be cured.

Referring to FIG. 4, a composite stringer charge 20 is placed on thecure tool 22. The stringer charge 20 comprises a hat 20 a filling thecavity 28 and engaging the tool face 32 (FIG. 3), and a pair oflaterally extending flanges 20 b respectively engaging the tool faces34. The stringer charge 20 may be laid up on a separate layup tool (notshown) and then transferred to the cure tool 22, or alternatively,depending on the geometry of the part charge , it may be possible tolayup the stringer directly on the cure tool 22.

Referring now to FIG. 5, after the stringer charge 20 has been placed inthe cure tool 22, a flexible bladder 30 is placed within the cavity 28(FIG. 4) of the stringer charge 20 in order to react autoclave pressuresthat are applied during a curing cycle. The bladder 30 may be formed ofany suitable material such, for example and without limitation, anelastomer. A release agent may be applied to the bladder 30 before it isinstalled to facilitate later removal of the bladder from the cavity 28following curing. The bladder 30 includes a bladder vent hole 44 that isadapted to be coupled with the fluid reservoir 32 shown in FIG. 1, aswill be discussed below. In this example, the bladder 30 is configuredto substantially match the geometry of the cavity 28 and has asubstantially flat upper surface 30 a that is substantially flush withthe flat tool surfaces 36 of the cure tool 22.

Referring now to FIG. 6, after the bladder 30 has been installed asshown in FIG. 5, a substantially flat composite skin charge 46 is placedon the cure tool 22, overlying the bladder 30 and in face-to-facecontact with the flanges 20 b (FIG. 5) of the stringer charge 20 and theflat tool surfaces 36. Next, as shown in FIG. 7, a caul plate 48 may beinstalled over the flat composite skin charge 46 in order to applysubstantially even pressure over the skin charge 46 during the curingprocess. Also, although not shown in FIG. 7, peel plies, release filmsand/or breathers or other components may be installed along with thecaul plate 48, depending on the application. As shown in FIG. 8, asuitable sealant tape 50 or other suitable sealant is applied to theperimeter of the cure tool 22 in preparation for vacuum bagging the tool22. At this point, a vacuum probe base 52 may be applied to the flat endsection 40 of the cure tool 22.

Next, as shown in FIG. 9, a flexible fluid reservoir 32 is attached tothe bladder 30 such that the bladder 30 and the fluid reservoir 32 maybe installed and removed as a single assembly, if desired. The fluidreservoir 32 is coupled with the vent hole 44 (FIG. 8) in the bladder 30and is supported on the chamfered surface 38 of the cure tool 22 whenthe bladder 30 is in place within the composite charge cavity 28. Thefluid reservoir 32 may be permanently attached and sealed to the bladder30, thus obviating the need to reconnect the bladder 30 to a pressuresource each time the bladder 30 is installed in a composite charge 20 inpreparation for a curing process. This arrangement also eliminates theneed for placing a sealant around the vent hole 44 each time the bladderis installed in a composite charge 20. The fluid reservoir 32 may befabricated from any suitable material such as, without limitation, anelastomer. A vacuum probe 54 is mounted on the vacuum probe base 52, andis adapted to be coupled with a vacuum source (not shown) for evacuatingthe vacuum bag 24 during a cure cycle.

Referring now to FIG. 10, the fluid reservoir may have a generallyrectangular or square cross sectional shape with sides 32 a that areflexible and may plastically deform inwardly as shown by the dashedlines 32 b when external pressure is applied to the fluid reservoir 32.A portion 32 b of the fluid reservoir 32 is attached in face-to-facecontact to one end of the bladder 30 and includes a fluid outlet 41 thatis aligned and coupled with the vent hole 44 in the bladder 30, allowingfluid to flow between the fluid reservoir 32 and the bladder 30. Inother embodiments, the fluid reservoir 32 may have a different shape,and may or may not be attached to the bladder 30. Following installationof the fluid reservoir 32 shown in FIG. 9, flexible bag 24, sometimesreferred to as a vacuum bag 24, formed of any suitable material such aspolyester or nylon, is installed over the tool 22, covering the fluidreservoir 32, the stringer charges 20, 46, and the bladder 30. Thevacuum bag 24 is in face-to-face contact with the fluid reservoir 32.The vacuum bag 24 is sealed to the periphery of the cure tool 22 andaround the vacuum probe using sealing tape 50 or other suitablesealants. Evacuation of vacuum bag 24 draws the vacuum bag 24 down inface-to-face contact with the sides of the fluid reservoir 32, allowingautoclave pressure P_(A) to be applied to the fluid reservoir 32.

Optionally, the fluid reservoir 32 may include a vacuum port 60 that isadapted to be coupled with a vacuum source (not shown) after the vacuumbag 24 has been removed following a cure cycle. The vacuum port 60 isclosed and sealed beneath the vacuum bag 24 during curing, but includesa valve or other device (not shown) that allows connection of theinternal volume 56 of the fluid reservoir 32 to the vacuum source aftercuring is completed and the vacuum bag has been removed. Coupling thefluid reservoir 32 to the vacuum source in this manner relieves fluidpressure within the fluid reservoir 32, which in turn reduces thepressure within the bladder 30, allowing the bladder 30 to deflate orcollapse slightly. Deflation of the bladder 30 in this manner reducesthe maximum cross sectional dimension (not shown) of the bladder 30 anamount that is sufficient to allow the bladder 30 to be removed from thecured stringer.

During curing carried out within an autoclave, autoclave pressure P_(A)forces the vacuum bag 24 against the cure tool 22, thereby compactingthe composite charge 20 while also applying pressure to the fluidreservoir 32. The autoclave pressure P_(A) applied to the fluidreservoir 32 causes fluid to flow 45 from the internal volume 56 of thefluid reservoir 32 through the bladder vent hole 44 into the bladder 30,thereby internally pressurizing the bladder 30. This pressurization ofthe bladder 30 causes a force 55 to be applied to composite charge 20that reacts the autoclave pressure P_(A) applied to the composite charge20. When curing is completed, the autoclave pressure P_(A) is removedfrom the vacuum bag 22, and thus is removed from the fluid reservoir 32.The resulting decrease in fluid pressure within the fluid reservoir 32allows fluid to flow from the bladder 58 through the vent hole 44 backinto the fluid reservoir 32.

As previously discussed, the fluid reservoir 32 may be permanentlysealed to the bladder 30, thus obviating the need to place a sealantaround the vent hole 44 (FIG. 8) each time the bladder 30 is installedin a composite charge 20. Permanently sealing the fluid reservoir 32 tothe bladder 30 may therefore eliminate leakage around the vent hole 44into the composite charge 20. In the event of a leak in either thebladder 30 or the fluid reservoir 32, fluid leakage into the compositecharge 20 is limited to the total volume of the bladder 30 and the fluidreservoir 32 since the bladder system 25 (FIG. 1) is a closed system anddoes not allow air from the autoclave to enter into the composite chargecavity 28 (FIG. 4).

An alternate embodiment of the disclosed non-vented bladder system isshown in FIGS. 11 and 12. In this embodiment, the bladder 30 includes aninternal septum 35 that separates the interior chamber 65 of the bladder30 from the fluid supplied by the fluid reservoir 32. The septum 35 ismade of a flexible material and may be formed integral with the bladder30. The bladder chamber 65 is filled with a flowable fill material 66having a relatively low CTE (coefficient of thermal expansion) and adensity selected to provide the bladder 30 with a desired level ofstiffness. One side 75 of the septum 35 is exposed to the fluid suppliedby fluid reservoir 32. Fluid from the reservoir 56 that is forcedagainst the bladder 30 by the autoclave pressure P_(A), exerts fluidpressure P_(F) (FIG. 12) against the septum 35, causing the septum 35 toflex inwardly to the position 35 a shown in FIG. 12, therebypressurizing the fill material 66. Pressurization of the fill material66 results in an outward pressure 68 being exerted against the compositecharge 20.

Referring now to FIG. 13, in the event of a leak in the non-ventedbladder system 25 described above, the volume of air within theautoclave 26 (FIG. 1) does not reach the composite charge 20, becausethe bladder system 25 is sealed beneath the vacuum bag 24. Rather, thetotal amount of fluid possibly reaching the composite charge 20 in theevent of a leak in either the bladder 30 or the fluid reservoir 32(FIGS. 10-12) is limited to the fluid reservoir interior volume 56 plusthe bladder chamber volume 65.

Attention is now directed to FIG. 14 which broadly illustrates the stepsof a method for autoclave curing using the non-vented bladder system 25described above. Beginning at step 70, a composite resin charge 20 isplaced on a suitable tool, which may be a cure tool. At 72, a flexible,inflatable bladder 30 is installed in an internal cavity 28 of thecharge 20. At 74, the flexible bladder 30 is coupled with a flexiblefluid reservoir 32 containing a quantity of fluid. At 76, the compositecharge 20 along with the fluid reservoir 32 are covered with a flexiblebag 24 such as a vacuum bag, which is then sealed to the cure tool 22.At 78, autoclave pressure P_(A) is applied to the bag 24 in order tocompress the fluid reservoir 32 and force fluid from the reservoir 32into the bladder 30, thereby pressuring the bladder 30 to react forcesapplied to the composite charge 20 by autoclave pressure. Optionally, atstep 80, an internal septum 35 within the bladder 30 may be employed totransmit pressure to the bladder 30 using the fluid pressure generatedby the fluid reservoir 32. Also, optionally at step 82, following curingand removal of the vacuum bag 24, pressure within the fluid reservoir 32may be relieved to aid in bladder removal, by coupling the fluidreservoir 32 with a suitable vacuum source.

An alternate method of curing a composite part charge 20 is shown inFIG. 15. At 84, a composite part charge 20 is placed on a tool 22, andat 86, a bladder 30 is installed in a cavity 28 of the composite partcharge 20. The bladder 60 is coupled with a reservoir of fluid 32 atstep 88. Next, as shown at step 90, a flexible bag 24 is sealed over thecomposite part charge 20 and the reservoir of fluid 32. At step 92, theflexible bag 24 is used to transmit autoclave pressure to the reservoirof fluid 32 to force fluid from the reservoir 32 into the bladder 60.

Embodiments of the disclosure may find use in a variety of potentialapplications, particularly in the transportation industry, including forexample, aerospace, marine, automotive applications and otherapplication where autoclave curing of composite parts may be used. Thus,referring now to FIGS. 16 and 17, embodiments of the disclosure may beused in the context of an aircraft manufacturing and service method 94as shown in FIG. 16 and an aircraft 96 as shown in FIG. 16. Aircraftapplications of the disclosed embodiments may include, for example,without limitation, curing of stiffener members such as, withoutlimitation beams, spars and stringers, to name only a few. Duringpre-production, exemplary method 94 may include specification and design98 of the aircraft 96 and material procurement 100. During production,component and subassembly manufacturing 102 and system integration 104of the aircraft 96 takes place. Thereafter, the aircraft 96 may gothrough certification and delivery 96 in order to be placed in service108. While in service by a customer, the aircraft 96 is scheduled forroutine maintenance and service 110, which may also includemodification, reconfiguration, refurbishment, and so on.

Each of the processes of method 94 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 17, the aircraft 96 produced by exemplary method 94 mayinclude an airframe 112 with a plurality of systems 114 and an interior116. Examples of high-level systems 114 include one or more of apropulsion system 118, an electrical system 120, a hydraulic system 122,and an environmental system 124. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosure may be applied to other industries, such as the marine andautomotive industries.

Systems and methods embodied herein may be employed during any one ormore of the stages of the production and service method 94. For example,components or subassemblies corresponding to production process 102 maybe fabricated or manufactured in a manner similar to components orsubassemblies produced while the aircraft 96 is in service. Also, one ormore apparatus embodiments, method embodiments, or a combination thereofmay be utilized during the production stages 102 and 104, for example,by substantially expediting assembly of or reducing the cost of anaircraft 96. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft96 is in service, for example and without limitation, to maintenance andservice 110.

The description of the different advantageous embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different advantageousembodiments may provide different advantages as compared to otheradvantageous embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A method of autoclave curing a composite chargehaving an internal cavity, comprising: placing the composite charge on atool; installing a bladder within the cavity; coupling the bladder witha reservoir of fluid; sealing a flexible bag over the composite chargeand the reservoir; and using the flexible bag to transmit autoclavepressure to the reservoir to force fluid from the reservoir into thebladder.
 2. The method of claim 1, wherein coupling the bladder with thereservoir includes attaching the bladder to the reservoir before thebladder is installed in the cavity.
 3. The method of claim 1, whereinsealing the bag includes sealing the bag to the tool.
 4. The method ofclaim 1, further comprising: stiffening the bladder by filling thebladder with a fill material, and separating the fill material from thefluid by placing a septum in the bladder.
 5. The method of claim 1,further comprising: using a vacuum to draw the flexible bag down againstsides of the reservoir.
 6. The method of claim 1, further comprising:removing the flexible bag from the composite charge and the reservoirafter the composite charge has been cured; and relieving pressure withinthe bladder by porting the reservoir to a vacuum source after theflexible bag has been removed.
 7. A method of autoclave curing acomposite part charge having an internal cavity, comprising: supportingthe composite part charge within the autoclave; and pressurizing abladder within the internal cavity using autoclave pressure to forcefluid from a fluid reservoir into the bladder.
 8. The method of claim 7,further wherein using the autoclave pressure to force the fluid from thefluid reservoir into the bladder includes: evacuating a vacuum bagsealed over the fluid reservoir, and using the bag to transmit theautoclave pressure to the fluid reservoir.